initialization of final fields

Thu Nov 4 06:44:00 GMT 1999

Hi Martyn,
I agree that the write*should* be performed just once, but again, the
pragmatic approach taken
by Sun is as I stated to avoid penalising the runtime (interpreter/JIT'd
code) ... so if gcj provides this,
it will be offering something that probably no other Java runtime does.
cheers, Jerry
----- Original Message -----
From: Martyn Pearce <m.pearce@inpharmatica.co.uk>
To: Jerry Kramskoy <Jerry.Kramskoy@insignia.com>
Cc: Martyn Pearce <m.pearce@inpharmatica.co.uk>; Per Bothner
<per@bothner.com>; Godmar Back <gback@cs.utah.edu>;
<java-discuss@sourceware.cygnus.com>; <vgp@dms.at>
Sent: Thursday, November 04, 1999 2:01 PM
Subject: Re: initialization of final fields
>> | > Pathological example I know, but... I don't think we've covered the
> | > possibility that a given initializer calls such a method more than
> | > once.
> | >
> | > Actually, I don't think it's so patholgical --- the method call might
be
> | > embedded in a loop without thinking.
>> Jerry Kramskoy writes:
> | Sun's stated semantics for writes to final fields are weaker than your
> | proposal ...
> | the current class (to which the executing method belongs)
> | must be the same as the declaring class for the final field.
>> I think we're at cross purposes here. I'm not thinking of which class
> the call is coming from, but how many times:
>> class MyClass
> {
> final int widget;
> int[] bar;
>> public
> MyClass (int count)
> {
> bar = new int[count];
> for (int i = 0; i < count; i++)
> this.init (i);
> }
>> private void
> init (int foo)
> {
> bar[foo] = 1;
> widget = foo;
> }
> }
>> Which is illegal (not to mention odd), since widget gets assigned to
> more than once, but I think that the scheme proposed by Per doesn't
> catch this.
>> I hasten to add that I don't suppose it'll occur that often, and that
> Per's scheme is several steps ahead of Sun's --- last I checked, jdk
> javac still can't handle indirect assignments to final fields (i.e.,
> assignments from methods called by the c'tor). Neither does jikes.
>> Mx.
>> PS: If there's still confusion about which part of the JLS is referred
> to here, the reader is directed to
>> http://java.sun.com/docs/books/jls/html/1.1Update.html
> D.1.2 New Uses for final
>> Paragraph 3:
>> 'You can defer initialization of a final field or variable, as long as
> you initialize it before it is used and assign a value to it exactly
> once. The compiler will check for proper assignment, as will the
> verifier before code is executed.'
>